United States whistleblower Chelsea Manning, who is yet to receive a visa from the Federal Government to enter Australia for a speaking tour, has gone ahead with a scheduled appearance at the Sydney Opera House via video link.

Ms Manning, formerly a soldier and intelligence analyst with the US military, spent seven years in jail for sending nearly 750,000 classified military and diplomatic documents to WikiLeaks.

The Australian organiser of her speaking tour, Think Inc, said on Thursday it had received a Notice of Intention to Consider Refusal under s501 of the Migration Act from the Australian government in regards to Ms Manning's visa.

Section 501 of the Migration Act allows the Minister to deny anyone a visa if they do not pass "the character test". Though Ms Manning has not had her visa refused, it had not been approved by Sunday.

Nonetheless, the appearance went ahead with the help of journalist Peter Greste, who interviewed Ms Manning from Sydney.

She discussed national security and privacy issues, her history as an intelligence analyst with the US military, the Iraq and Afghanistan wars, and queer and trans issues.

Data breaches 'features of the system, not bugs'

Ms Manning said data breach scandals like the recent Cambridge Analytica debacle, or Facebook's sharing of data, was "business as usual".

She said she was not defending it all, however that was "the [business] model … it shouldn't be shocking at all" but something had to be done.

"These are features in the system, not bugs."

'It shattered my understanding of the world'

An advocate for queer and trans rights, Ms Manning said the Proposition 8 referendum in California which quashed same-sex marriage in the state, despite its previous legalisation, shocked her and her sense of the world.

"[Marriage equality] been made legal through the court process here and that was undone. Largely the way I viewed it [was] that 51 point something per cent [of people] … [wanted] to effectively divorce, at the time, 11,000 people," she said.

"I had been living under this assumption history is over, things are always going to get better … it challenged that, it really shattered my understanding of the world and of institutions being benevolent."

She said queer and trans issues were systemic, and court processes were not enough to better LGBT rights.

'Please don't deadname me'

A few minutes into the discussion, Greste was pulled up by Ms Manning, a transgender woman, for using her "deadname" — a term for Ms Manning's pre-transition name — and used male pronouns, when referring to her time in the military.

"Please don't deadname me," she said.

The interruption was met with cheers and applause from the audience, but she then moved on with the interview to discuss more about her time in the US military.

Ms Manning said she joined the military thinking of "Iraq and Afghanistan as being equations that can be solved."

However, when she was deployed to Iraq in 2009, her view of the war changed drastically.

"Once [you're] immersed in a war zone you realise just how … it wasn't statistics anymore," she said.

"These were people with lives and flaws and all of the vulnerabilities people have. All the hopes and dreams and the mistakes that are made … life and death."